A semiconductor physical quantity sensor having a detection electrode for detecting static capacitance is disclosed in JP-A-2000-31502 corresponding to US Patent Application Publication No. 2001/0029060. The sensor is made from a SOI wafer, and the electrode is made of single crystal silicon. Specifically, the sensor includes a beam structure having a movable electrode displaceable in accordance with acceleration. The displacement of the beam structure provides capacitance change of a capacitor formed by the movable electrode and a fixed electrode, which is fixed on a substrate. The sensor detects the acceleration based on the capacitance change so that the sensor is a capacitive acceleration sensor.
The fixed electrode in the sensor is provided by a fixed portion. The fixed portion includes a wiring, on which an output terminal is arranged. The output terminal is electrically coupled with an external circuit. The fixed portion is formed in a SOI layer, and the output terminal is made of aluminum or the like. Accordingly, the fixed portion in the SOI layer is formed with using a special photo lithography mask. The output terminal is formed with using another special photo lithography mask. Thus, it is necessary to perform two photo lithography processes for manufacturing the sensor. One is for the fixed portion and the other is for the output terminal.
Thus, the number of processes is increased. Further, since each photo lithography process includes multiple steps, the manufacturing man-hour of the sensor increases. Further, since the different photo lithography masks are used in two processes, it is necessary to align the mask in each process. Accordingly, if a position of each mask is deviated from an appropriate position, the output terminal may not be formed on a predetermined area on the wiring. Thus, a manufacturing yield of the sensor may be reduced.
Thus, it is required for the sensor to align the masks for the fixed portion and the output terminal with high accuracy.